Trees used to create lumber and other wood products may be straight, curved, also called swept, or tapered, or a combination of the three. Much work has been done to maximize the board feet of lumber that can be obtained from imperfect logs, in particular ones which are tapered and curved. These problems are especially acute when smaller diameter logs are used. A number of issued patents attempt to address the problems of curved and tapered logs. See, for example, U.S. Pat. Nos. 5,761,979; 4,239,072; 4,449,557; 5,816,302; 5,853,038; and 5,946,995. See also U.S. patent application Ser. No. 09/792,891 filed Feb. 23, 2001, which claims the benefit of provisional patent application No. 60/184,422 filed Feb. 23, 2000. Controllers have been developed to control these complicated saw milling equipment. See, for example, U.S. Pat. No. 5,884,682.
The present invention is directed to a log processor and log processing method which permit optimal production of sawed products from logs which are straight, curved, tapered, or a combination thereof, quickly and effectively.
A first aspect of the invention is directed to a log processing method during which a log is passed along a feed line from a log entrance to a log exit. The log is scanned at a first station. The longitudinal centerline and a sawing scheme for the log are automatically determined by a controller based at least in part on the results of the scanning step. The sawing scheme includes a saw blade path through the log which often is but may not be parallel to the longitudinal centerline of the log. The log is oriented at a second station along the feed line so that the longitudinal centerline is oriented with respect to a chosen plane. A chosen plane is typically a vertical plane passing through the feed line. The log is engaged at third and fourth stations along the feed line. The position of the longitudinal centerline of the log relative to the feed line and the chosen plane is automatically adjusted so that the saw blade path of the log at the log exit is generally parallel to the feed line as the log passes the log exit. The log is driven past a saw at or adjacent to the log exit to create the board or other sawed product.
The sawing scheme can include variable tapering sawing from split taper sawing to full taper sawing. The position-adjusting step may include the use of generally hourglass-shaped differential centering rolls at the third station and differential steering chain assemblies at the fourth station. The differential steering chain assemblies may each include continuous loop, log-engaging chains having log-engaging sections which engage the log, typically above and below the log. Log chipping, profiling heads may be used on either side of the feed line, such as at a fifth station. The log is preferably stabilized at the log exit.
Another aspect of the invention is directed to a log processor including a controller and log conveyor assembly operably coupled to the controller. The log conveyor assembly includes a log entrance, at which a log is introduced to the conveyor assembly at one end of a feed line, and a log exit, at the other end of the feed line. The assembly includes a log scanner at a first station which determines a longitudinal centerline and a sawing scheme for the log. The sawing scheme includes a saw blade path through the log. A log orienting assembly is at second station and is configured to orient the scanned log to a chosen orientation with a longitudinal centerline of the log oriented with respect to, and typically aligned with, a chosen plane. The assembly further comprises first and second log positioners at third and fourth stations along the feed line. The log positioners continuously position the log as the log passes through the third and fourth stations so that as the log passes the log exit, the saw blade path is generally parallel to the feed line to help ensure the log is fed properly into a saw located at or adjacent to the log exit.
The first log positioner may include first and second differential centering rolls coupled by a linkage assembly so that the centering rolls move in equal amounts but in opposite directions; this permits the longitudinal centerline to remain centered between the centering rolls as the diameter of the log changes. The second log positioner may include first and second chain assemblies moveably mounted to the frame, each chain assembly including a chain support, a continuous loop, log-engaging chain mounted to the chain support, and an angular orientation assembly supportably mounting the chain assembly to the frame. The second log positioner may also include a differential gap assembly coupling the angular orientation assemblies to one another and biasing the log-engaging sections towards an initial separation. The log processor may also include log chippers located on opposite sides of the feed line. One type of log chipper may include side chipping heads located at the fourth station having effectively flat cutting faces oriented at least generally parallel to the chosen lane. Another type of log chipper may include profiling heads located at a fifth station, at least one of the profiling heads may include a number of rotatable cutting elements. Steering rolls or other log stabilizers may be used at the log exit.
A further aspect of the invention is directed to a log steering assembly for use with a log processor of the type having a stationary frame. The log steering assembly includes first and second chain assemblies movably mounted to the frame on opposite sides of the feed line of the log processor for movement toward and away from and at angles relative to the feed line. Each chain assembly includes a chain support and a continuous loop, log-engaging chain mounted to the chain support and passing along a chain path, the chain path including an elongated log-engaging section. Each chain assembly also includes an angular orientation assembly mounting the chain assembly to the frame at a selected angular orientation relative to the feed line. The log steering assembly may also include a differential gap assembly coupling the angular orientation assemblies to one another and biasing the log engaging sections towards an initial separation. The angular orientation assembly may include first and second bell cranks, each bell crank connected to the chain support and to the frame, and an adjustable link connecting the bell cranks so that changing the length of the link changes the relative angular orientation of the bell cranks and thus the angular orientation of the chain support.
Other features and advantage of the invention will appear from the following description in which the preferred embodiments have been set forth in detail in conjunction with the accompanying drawings.